"
Unnecessary speed or acceleration"
If that isn't the description of an action that would be the widest, most broadly interpreted thing ever. That truly does leave it up to the officer in charge to decide if what you were doing wasn't simply "speeding", but was
unnecessary.
In fact, not closely that it doesn't say
excessive or beyond the speed limit "speed"...they could interpret that as being something like "unnecessary for the conditions".
My daughter got warned for overtaking a slow caravan in the rain on a long straight stretch of highway with good visibility. A police car coming the other way flashed the lights and did a u-turn. She pulled over, and started wondering if she had been speeding, but instead the cop merely gave her a warning and a short talk about how bad it was to be driving quickly in the rain, especially overtaking, and that even the legal limit may be too much in some circumstances. He considered that what she was doing was, in a word, "unnecessary"...
I know other people that have had similar, and also ex-coppers I work with confirm that if they think you are driving "too fast for the conditions" you don't even have to be speeding...as long as it's considered "dangerous" at the time.
Have a little think about your daily drive...even without speeding, is what you are doing "unnecessary" for the conditions...?